Health calculator
BMI Calculator
Calculate Body Mass Index with metric or US units, then see the adult BMI category, health risk, normal BMI range, and estimated healthy weight range.
BMI category scale
Adult category thresholds are commonly interpreted as underweight below 18.5, normal 18.5-24.9, overweight 25-29.9, and obesity 30 or above.
BMI categories table for adults age 20 and older
| BMI category | BMI range | Health risk |
|---|---|---|
| Underweight | 18.4 and below | Malnutrition risk |
| Normal weight | 18.5 - 24.9 | Low risk |
| Overweight | 25 - 29.9 | Enhanced risk |
| Moderately obese | 30 - 34.9 | Medium risk |
| Severely obese | 35 - 39.9 | High risk |
| Very severely obese | 40 and above | Very high risk |
BMI categories for kids and teens under age 20
| BMI category | BMI percentile | Health risk |
|---|---|---|
| Underweight | Less than 5th percentile | Malnutrition risk |
| Normal weight | 5th percentile to less than 85th percentile | Low risk |
| Overweight | 85th percentile to less than 95th percentile | Enhanced risk |
| Obese | 95th percentile and greater | High risk |
This calculator shows adult BMI categories. Pediatric BMI should be interpreted with age-and-sex growth charts.
BMI formula
Metric formula: BMI = weight(kg) / height(m)^2.
US formula: BMI = 703 x weight(lb) / height(in)^2.
Normal weight range is estimated by solving the metric formula for BMI 18.5 to 24.9 at the entered height.
FAQ
Is BMI accurate for everyone?
No. BMI does not directly measure body fat and can be less informative for athletes, older adults, pregnant people, or people with unusual muscle mass.
Why ask for age and sex?
Adult BMI categories are the same here, but children and teens require percentile interpretation based on age and sex. The inputs make that limitation visible.
Does this replace medical advice?
No. It is a general calculator for education and planning. Talk to a qualified health professional for medical guidance.